1. Field of the Invention
This invention relates to glycoside materials.
2. Description of the Art Practices
It has long been known that alkyl glycosides have surfactant properties and are therefore desirable as either the sole surfactant, or in combination with other surfactants, in cleaning products. A glycoside as used herein means a material which contains 1 or more units of a sugar source such as glucose and a hydrophobic organic tail. If the glycoside contains glucose units, then it is referred to as a glucoside. If the glycoside contains 2 units of glucose, e.g. a polymer, then the material is referred to as a glycoside having a degree of polymerization (D.P.) of 2. If the glycoside is an alkyl glycoside then the material is substituted in the one position with an alkoxyl moiety rather than the C.sub.1 hydroxyl of the starting sugar. Therefore, the attachment of the alkoxyl moiety is by an acetal linkage to the sugar.
It has been suggested by Boettner in U.S. Pat. No. 3,219,656 issued Nov. 23, 1965 that an acid catalyzed route for obtaining an alkyl polyglycoside (APG) may be utilized starting with a saturated alcohol and dextrose. Similarly, Mansfield in U.S. Pat. No. 3,547,828 issued Dec. 15, 1970 teaches a method of obtaining glycosides.
U.S. Pat. No. 3,974,138 issued to Lew on Aug. 10, 1976 states that it is preferable to use glucose as a starting material for the preparation of butyl polyglycoside. It has been observed, according to Lew, that it is extremely difficult when starting with the sugar source to obtain higher alkyl polyglycosides directly. That is, the starting sugar materials are highly water-soluble whereas dodecyl alcohol (to add a C.sub.12 group) is extremely water-insoluble. Therefore, the route proposed by Lew is to form an intermediate butyl glycoside and to thereafter transetherify to obtain the higher alkyl polyglycosides. In such a reaction, butyl alcohol is generated as a by-product.
The removal of alcohols formed in transetherification is described by Mao in U.S. Pat. No. 4,393,203 issued July 12, 1983. In the disclosure, Mao states that it is desirable to remove the alcohol formed because of its adverse effect on the surfactant properties of the alkyl polyglycoside. Mao further states that the color properties of his product are not adversely affected by the processing described in his patent.
European Patent Application No. 82305283.5, published as 0077167 on Apr. 20, 1983 states that various reducing agents may be utilized in the processing of alkyl polyglycosides. The teachings of the 0077167 publication are that the reducing agent must be present with an acid catalyst which is used to react the alcohol with an aldose or ketose. The reducing agents stated to be useful are acids such as phosphorous, hypophosphorous, sulfurous, hyposulfurous, nitrous and hyponitrous acids. It is further stated that the composition containin the reducing agent remains in the acid form.
European Patent Application No. 83200771.0 published on Dec. 28, 1983 as 0096917 to Farris describes the preparation of alkyl glycosides using an acid catalyst at from 80.degree. C. to 150.degree. C. The 0096917 publication further states that a long-chain monohydric alcohol is used to form the glycoside by continuously or incrementally adding the monosaccharide and catalyst such that no more than 10% by weight of unreacted monosaccharide is present at any given time and that the average amount of unreacted monosaccharide not exceed 5% by weight of the mix. The stated reason for controlling the amount of saccharide present in the reaction mix of Farris is so that there is substantially a single phase present. U.S. Pat. No. 3,450,690 to Gibbons issued June 17, 1969 discusses the use of alkaline materials to remove alkali sensitive color bodies from an alkyl glucoside mixture.
European published application No. 102,558 discloses borates as being useful in preparing glycosides. It is further known that N-methyl-2-pyrrolidone may be utilized as a reaction medium to obtain a substantially single phase reaction between a saccharide and an alcohol to form an alkyl glycoside. It is also known that long-chain alkyl glycosides may be formed directly from a saccharide by utilizing a small amount of a previously prepared long-chain alkyl glycoside to render the saccharide and the alcohol compatible.
It has been disclosed in European published application No. 0099183 of Short (Jan. 25, 1984) that saccharides may be converted into glycosides of up to 6 carbon atoms by forming a liquid dispersant system containing the monohydric alcohol to be added. The liquid dispersant system includes acetone, ethylene glycol, methanol or ethanol and about 2 to 25 moles of water per saccharide molar unit. This reaction is stated to take place at superatmospheric pressure to maintain the dispersants in a liquid state.
The art has recognized several methods of obtaining and treating glycosides, yet color of the end product remains a problem. There has as yet not been an effective manner of maintaining a glycoside in a desirable lightly colored state. That is, alkyl glycosides as obtained are a dark amber color and for many uses, such as cosmetics or detergent products, it is desirable that they have no more than a straw yellow color.
It has been observed herein that even in products which have been decolorized that the color will degrade in the product upon standing. Therefore, it is desirable, and the present invention deals with, obtaining and stabilizing good color in alkyl glycosides.
Throughout the specification and claims, percentages and ratios are by weight, temperatures are degrees Celsius and pressures are in atmospheres over ambient unless otherwise indicated.
To the extent that such references are applicable, each of the foregoing is incorporated herein by reference.